Scientists at Nanyang Technological University in Singapore have cracked a problem that has stymied recyclers for decades: how to separate and reuse the mixed plastics bonded together in everyday food packaging. The innovation, called DIPS (depolymerization-induced polymer separation), uses no harmful chemical solvents and works in standard manufacturing equipment, opening a pathway to recycle one of the world's most troublesome waste streams.
Mixed plastic packaging—the multilayered material wrapping snacks, instant noodles, and countless other food products—was designed to be tough and airtight. That very durability makes it nearly impossible to separate and recycle. Most of it ends up in landfills or incinerators, contributing to a mounting global waste crisis. With plastic production projected to reach 736 million tons by 2040, the stakes for solving this problem have never been higher.
The team from NTU Singapore's School of Materials Science and Engineering and Nanyang Environment and Water Research Institute developed DIPS using a technique called reactive extrusion. The process works by feeding mixed packaging into an industrial extruder—a machine commonly used to melt and shape plastics—where it becomes a chemical reactor. When the extruder heats the mixed material, polyethylene terephthalate (PET), the plastic used in drink bottles, reacts with glycerol, a cheap and widely available substance. This chemical reaction transforms the PET into smaller molecules with fundamentally different properties, causing it to naturally separate from polypropylene (PP), another plastic in the mix. The separation happens automatically, driven by differences in polarity and viscosity, without adding any solvents or requiring special pressure conditions.
Lead investigator Professor Hu Xiao noted that the team developed the method because "recycling it safely and efficiently is still a major challenge." The results validate that approach. In laboratory tests using post-industrial mixed packaging waste, the recovered polypropylene retained mechanical properties remarkably close to virgin plastic, achieving up to 90% of its original tensile strength under optimal conditions. That strength matters: it means the recycled material is genuinely strong enough for practical reuse, not degraded into lower-value applications.
The recovered PET, while not directly reusable in its original form, contains chemical groups that make it suitable for higher-value uses—potentially replacing epoxy in wind turbine blades or serving as a building block for other polymers. The researchers believe DIPS can be extended to other mixed plastic combinations and scaled up using the same extruders already common in factories worldwide, avoiding the need for entirely new infrastructure.
Co-author Dr. Liang Yen Nan emphasized that "the lack of a viable way to deal with mixed plastics" has been the central challenge driving innovation in the field. If mixed plastic waste were efficiently recycled at scale, it could unlock substantial economic value while dramatically reducing the volume of packaging destined for landfills. What began as a laboratory experiment addressing one of recycling's thorniest problems may soon become a practical tool for transforming industrial waste into usable material—a shift that could reshape how the world handles its plastic future.